Early morning is the best as I've said before. There's nothing like beginning the day with the sunrise. But find your own rhythm. If there's people in your life who like to talk, it's wonderful to be with them late, late at night when thoughts move away from the workaday world towards the esoteric. But there's no point forcing yourself into anything. The body has its own needs and rhythms. However, if you want to become an early riser, sleep this spring in an east-facing room. Open the curtains and let the light in. There's a lot of bioscience around light and darkness. Google around a bit. They say darkness produces melatonin to help us become drowsy.
The theory behind dawn simulation is that early morning light signals have a much greater effect on the body’s biological clock than light signals given at other times during a day.